Energy-momentum for a charged nonsingular black hole solution with a nonlinear mass function

The energy-momentum of a new four-dimensional, charged, spherically symmetric and nonsingular black hole solution constructed in the context of general relativity coupled to a theory of nonlinear electrodynamics is investigated, whereby the nonlinear mass function is inspired by the probability density function of the continuous logistic distribution. The energy and momentum distributions are calculated by use of the Einstein, Landau-Lifshitz, Weinberg and M{\o}ller energy-momentum complexes. In all these prescriptions it is found that the energy distribution depends on the mass $M$ and the charge $q$ of the black hole, an additional parameter $\beta$ coming from the gravitational background considered, and on the radial coordinate $r$. Further, the Landau-Lifshitz and Weinberg prescriptions yield the same result for the energy, while in all the aforesaid prescriptions all the momenta vanish. We also focus on the study of the limiting behavior of the energy for different values of the radial coordinate, the parameter $\beta$, and the charge $q$. Finally, it is pointed out that for $r\rightarrow \infty$ and $q = 0$ all the energy-momentum complexes yield the same expression for the energy distribution as in the case of the Schwarzschild black hole solution.Comment: 20 pages, 4 figures, two of the figures changed, Discussion modified accordingly, present version accepted for publication in AHE

Decoupling of the general scalar field mode and the solution space for Bianchi type I and V cosmologies coupled to perfect fluid sources

The scalar field degree of freedom in Einstein's plus Matter field equations is decoupled for Bianchi type I and V general cosmological models. The source, apart from the minimally coupled scalar field with arbitrary potential V(Phi), is provided by a perfect fluid obeying a general equation of state p =p(rho). The resulting ODE is, by an appropriate choice of final time gauge affiliated to the scalar field, reduced to 1st order, and then the system is completely integrated for arbitrary choices of the potential and the equation of state.Comment: latex2e source file,14 pages, no figures; (v3): minor corrections, to appear in J. Math. Phy

TRANSFORMING GEOLOGICAL AND LANDISLIDE SUSCEPTIBILITY MAPPING DATA TO LINKED (OPEN) DATA FOR HAZARD MANAGEMENT

Η έλλειψη ενημέρωσης για τους πληθυσμούς που είναι εκτεθειμένοι σε κατολισθητικούς κινδύνους είναι μια κοινωνικο-οικονομική συνιστώσα της τρωτότητας του κοινωνικού ιστού και μπορεί να αυξήσει τον κίνδυνο απώλειας ζωών και υποδομών. Οι χρήστες αυτών των πληροφοριών χρειάζονται πολλά δεδομένα από κατολισθητικές περιοχές έτσι ώστε να καταστήσουν τις υπάρχουσες υποδομές πιο ανθεκτικές σε πιθανό καταστροφικό συμβάν. Πιο συγκεκριμένα, οι ιδιωτικοί και δημόσιοι οργανισμοί θα έχουν πχ τη δυνατότητα να επιλέξουν μεταξύ διαφορετικών χρήσεων γης για να ελαχιστοποιηθεί ο κίνδυνος υπαρχόντων υποδομών ή για τη μείωση του ίδιου του κινδύνου (μέσω μέτρων άμβλυνσης του). Από την άλλη πλευρά, οι χωροτάκτες μπορούν να πάρουν πιο ρεαλιστικές αποφάσεις πριν να προγραμματίσουν νέες υποδομές, σε 1684 περιοχές με υψηλό κατολισθητικό κίνδυνο. Έχουμε εφαρμόσει νέα εργαλεία για να αναπτύξουμε υπηρεσίες που είναι διαθέσιμες σε κάθε ενδιαφερόμενο, για τον εντοπισμό περιοχών επιδεκτικών σε κατολισθήσεις και που βασίζονται σε διαδικτυακές υπηρεσίες προκειμένου να παράσχουμε στους ενδιαφερόμενους φορείς πολύτιμες πληροφορίες σχετικά με την παλιότερη κατανομή των κατολισθήσεων σε μια περιοχή, τον τύπο των πετρωμάτων, τις βροχοπτώσεις κλπ με σκοπό να διαμορφώσουν πολιτικές χρήσης και να αξιολογήσουν μια επικείμενη κατολίσθηση.The frequent lack of information to populations exposed to landslides is a component of the social vulnerability and can strongly increase the risk on lives and infrastructures. Determining the extent of the landslide hazard requires identifying those areas which could be affected by a damaging landslide. The users need to integrate different landslide data in order to first understand and then possibly become resilient to any potential catastrophic event. More precisely, public and private organizations can choose between different land use options to minimize the risk on the already existing infrastructures or to reduce the hazard itself through mitigation measures. From the other hand, the land use planners can also take best decisions before planning new infrastructures in high risk landslides’ areas. Based on these data we have also implemented new tools, available every day and reusable by anyone interested, to identify land areas susceptible for landslides. The tools are based on cloud web services, especially for the management and presentation of these datasets in order to provide stakeholders with valuable information about past distribution of the landslides, type of bed rock, rainfall etc. in order to focus on land use policies and assess an impending landslide.

On the energy of a non-singular black hole solution satisfying the weak energy condition

The energy-momentum localization for a new four-dimensional and spherically symmetric, charged black hole solution that through a coupling of general relativity with non-linear electrodynamics is everywhere non-singular while it satisfies the weak energy condition is investigated. The Einstein and M\{o} ller energy-momentum complexes have been employed in order to calculate the energy distribution and the momenta for the aforesaid solution. It is found that the energy distribution depends explicitly on the mass and the charge of the black hole, on two parameters arising from the space-time geometry considered, and on the radial coordinate. Further, in both prescriptions all the momenta vanish.In addition, a comparison of the results obtained by the two energy-momentum complexes is made, whereby some limiting and particular cases are pointed out.Comment: 20 pages, 9 figure

Using cool paving materials to improve microclimate of urban areas e Design realization and results of the flisvos project

The present paper deals with the application of 4500 m2 of reflective pavements in an urban park in the greater Athens area. The aim was to improve thermal comfort conditions, reduce the intensity of heat island and improve the global environmental quality in the considered area. To our knowledge, this has been the largest application of cool pavements in urban areas in the world. To evaluate the thermal impact of cool paving materials, specific and detailed measurements of the climatic conditions in the park have been performed before and after the installation of the new materials. Validated computerized fluid dynamics techniques have been used to homogenize the boundary conditions occurring during the two experiments and to perform direct comparisons of the climatic quality in the park. It was estimated that the use of cool paving materials contributes to the reduction of the peak ambient temperature during a typical summer day, by up to 1.9 K. At the same time, the surface temperature in the park was decreased by 12 K, while comfort conditions have been improved considerably. It is concluded that the use of reflective paving materials is a very efficient mitigation technique to improve thermal conditions in urban area

Towards Canonical Quantum Gravity for G1 Geometries in 2+1 Dimensions with a Lambda--Term

The canonical analysis and subsequent quantization of the (2+1)-dimensional action of pure gravity plus a cosmological constant term is considered, under the assumption of the existence of one spacelike Killing vector field. The proper imposition of the quantum analogues of the two linear (momentum) constraints reduces an initial collection of state vectors, consisting of all smooth functionals of the components (and/or their derivatives) of the spatial metric, to particular scalar smooth functionals. The demand that the midi-superspace metric (inferred from the kinetic part of the quadratic (Hamiltonian) constraint) must define on the space of these states an induced metric whose components are given in terms of the same states, which is made possible through an appropriate re-normalization assumption, severely reduces the possible state vectors to three unique (up to general coordinate transformations) smooth scalar functionals. The quantum analogue of the Hamiltonian constraint produces a Wheeler-DeWitt equation based on this reduced manifold of states, which is completely integrated.Comment: Latex 2e source file, 25 pages, no figures, final version (accepted in CQG

Energy-Momentum Localization for a Space-Time Geometry Exterior to a Black Hole in the Brane World

In general relativity one of the most fundamental issues consists in defining a generally acceptable definition for the energy-momentum density. As a consequence, many coordinate-dependent definitions have been presented, whereby some of them utilize appropriate energy-momentum complexes. We investigate the energy-momentum distribution for a metric exterior to a spherically symmetric black hole in the brane world by applying the Landau-Lifshitz and Weinberg prescriptions. In both the aforesaid prescriptions, the energy thus obtained depends on the radial coordinate, the mass of the black hole and a parameter $\lambda_{0}$, while all the momenta are found to be zero. It is shown that for a special value of the parameter $\lambda_{0}$, the Schwarzschild space-time geometry is recovered. Some particular and limiting cases are also discussed.Comment: 10 pages, sections 1 and 3 slightly modified, references modified and adde

Distribution of Energy-Momentum in a Schwarzschild-Quintessence Space-time Geometry

An analysis of the energy-momentum localization for a four-dimensional\break Schwarzschild black hole surrounded by quintessence is presented in order to provide expressions for the distributions of energy and momentum. The calculations are performed by using the Landau-Lifshitz and Weinberg energy-momentum complexes. It is shown that all the momenta vanish, while the expression for the energy depends on the mass $M$ of the black hole, the state parameter $w_{q}$ and the normalization factor $c$. The special case of $w_{q}=-2/3$ is also studied, and two limiting cases are examined.Comment: 9 page